A network equipment system in which a plurality of network devices are connected to each other through telecommunications lines such as the Internet and they perform a predetermined action in concert with each other has been provided. For example, a system in which a home server and various equipment devices in a home (for example, an information display device, an air-conditioning control device, and so on) are connected to each other through the Internet and which controls the equipment devices in the home and/or monitors the power in the home through the Internet has been provided.
Heretofore, in order to design such a system, an object-oriented language is widely used. The object-oriented language has features such as encapsulation, inheritance, polymorphism, and it is effective for especially a large-scale software development.
When a new network device is added to a network equipment system constituted by the object-oriented language, it is necessary to examine the influence of the new network device upon the whole system, and it requires a lot of time and effort as the system becomes complex. This is because the objects in the object-oriented language operate while interacting with each other, and when an object is added, the states of other objects are influenced by the added object. If the investigation of the system is imperfect, so-called deadlock may occur. Therefore, as the system becomes complex, it becomes difficult to add a new network device to the network equipment system constituted by the object-oriented language. Furthermore, because the object has much internal state information, if a problem arises in investigating the system, it is necessary to identify the internal state information and to re-create the state in order to re-create the problem, so, debugging is not easy.
By the way, Japanese Non-examined Patent Publication No. 8-137697 discloses an autonomous distributed system in which a plurality of agents communicate and work together to process a task according to a predetermined system characteristics. In this distributed system, a problem of a whole system is decomposed (broken down) into subproblems capable of being resolved independently, and each agent determines its share of the subproblems by negotiation. Each subproblem is configured so that it is does not depend on other subproblems and a result of each subproblem is not required for other subproblems. In this autonomous distributed system, it is described that it becomes easy to maintain the system, such as a change of a system configuration, because each agent resolves a problem autonomously.
So, in order to deal with a system change easily, it is conceivable to apply such an autonomous distributed system to the above-mentioned network equipment system. However, in the above network equipment system, because it is difficult to decompose a problem of a whole system into subproblems and there is a dependence relationship between the decomposed subproblems, it is difficult to apply the autonomous distributed system of the above publication.